🌱 Why Your Cannabis Plants Aren’t Growing (and Simple Fixes You Can Try)

🌤️ 1) Not Enough Light

Light is the engine of growth. If intensity or duration is too low, plants stretch and slow down.

What to look for

• Tall, thin internodes (“stretching”)
• Pale/new growth lacking vigor
• Slow or stalled new shoots

Simple fix: For indoor cannabis, aim for:

• Vegetative: 18/6 light cycle (or 20/4); moderate PPFD (~300–500 µmol/m²/s)
• Flower: 12/12 light cycle; higher PPFD (~600–900 µmol/m²/s)

Raise intensity gradually and keep LEDs at the manufacturer’s recommended hanging height. Rotate plants weekly for even coverage.

💧 2) Overwatering or Underwatering

Roots need moisture and oxygen. Too wet = low oxygen; too dry = nutrient transport slows.

Overwatering signs: droopy leaves while soil is wet, slow growth, fungus gnats.
Underwatering signs: dry, hydrophobic soil; crispy edges; wilt that perks up right after watering.

Simple fix: Water only when the top 2–3 cm (about 1 inch) of medium is dry. Lift the pot — light = time to water. Ensure drainage holes, avoid standing water in saucers, and consider adding perlite to soil or using fabric pots for better aeration.

🌱 3) Nutrient Imbalance

Cannabis needs different nutrient profiles by stage: more N in veg, and more P/K in flower. Too little slows growth; too much can burn roots and lock out other minerals.

What to look for

• Pale or yellowing lower leaves (possible N deficiency)
• Weak stems and thin growth
• Burnt tips or dark, clawing leaves (possible excess)

Simple fix: Use a cannabis-friendly, balanced feed and follow the low end of the schedule:

• Veg: gentle, N-forward formula
• Flower: reduce N, increase P/K

Start at 50% of the label dose and observe 7–10 days. When in doubt, less is more.

⚖️ 4) pH Out of Range

Even with the right nutrients, incorrect pH blocks uptake and stalls growth.

Target pH ranges

• Soil: 6.0–7.0
• Coco/Hydro: 5.8–6.2

Simple fix: Test runoff or reservoir pH with a meter or drops. Adjust gradually using pH up/down. If lockout is suspected, flush with pH-balanced water, then resume a light feeding at the correct pH.

🌡️ 5) Temperature or Humidity Issues

Environment drives metabolism. Too hot, cold, or dry/wet and plants shift energy from growth to survival.

What to aim for (indoor)

• Vegetative: 22–28 °C (72–82 °F), RH ~50–65%
• Flower: 20–26 °C (68–79 °F), RH ~40–55%

Simple fix: Use an oscillating fan for airflow, exhaust hot air at the top of the tent/room, and avoid cold drafts. A small humidifier/dehumidifier helps keep RH in range and reduces stress.

🌿 6) Rootbound or Limited Root Zone

Restricted roots = restricted shoots. When the root mass circles the pot, water/nutrient access and stability drop.

What to look for

• Roots circling the pot edges/drain holes
• Water runs through too fast
• Stunted growth despite healthy color

Simple fix: Up-pot to a container 2–3 inches wider (or move from 1–3 gal to 5–7 gal, depending on plant size and veg time). Loosen circling roots gently and add fresh, aerated medium.

☀️ 7) Photoperiod & Seasonal Notes

Photoperiod cultivars rely on day length to flower; autoflowers don’t. Outdoors, short days trigger bloom; indoors you control it with timers.

• Photoperiod: Veg under 18/6; switch to 12/12 to flower
• Autoflower: Typically 18–20 hours of light from seed to harvest

Simple fix: Verify timers, eliminate light leaks during dark periods, and keep schedules consistent.

🌾 Quick Summary